An optical device has an optical modulator element and an optical receiver element. The optical modulator element includes a first optical waveguide extending to a first end face, a first inter-element waveguide extending to a second end face, and an optical modulator including an electro-optic material. The optical receiver element includes a second optical waveguide extending to a third end face, a second inter-element waveguide extending to a fourth end face, an optical receiver, and a polarization element. In the optical device, the first inter-element waveguide and the second inter-element waveguide have been connected to each other by being butted against each other.